1. Field of the Invention
The present invention relates to a screw, in particularly a bimate screw.
2. Description of the Related Art
Referring to FIG. 1, a conventional screw 1 comprises a shank 12, a head 11 disposed on one side thereof, a distal end 13 on the other side thereof, and a first threaded section 14 and a second threaded section 16 spirally arranged on the shank 12; wherein the two threaded sections 14, 16 alternate with each other. While screwing, the end 13 is initially drilled into the object 2, and the two threaded sections 14, 16 assist to cut the fibers so that the screw 1 can be screwed into the object 2.
Generally, in view of the two threaded sections 14, 16 and the threads thereof, the object fibers and debris may not be thoroughly cut and shattered, which results of those cuttings being normally twisted round the shank 12 and increasing the screwing resistance. Further, the cuttings may be hardly guided out, namely they would be incessantly accumulated in the object 2 and the movement thereof would also be interfered while screwing so that both the object 2 and the screw 1 would be facilely damaged or broken under the pressure of the accumulation. Subsequently, the screw 1 may be successfully screwed into the object 2 but may not substantially embed itself therein. That is, the threads merely push fibers away from their places but do not firmly catch them for a good holding force after screwing in, and the screw 1 thus is turned back toward the surface of the object 2 in response to the resilience of the object fibers and the external force imparted to the object 2, e.g. the vibration on the object; therefore, the objects fastened by the screw 1 would be loose or even fall over and which hence harms the users.